Conductive polymer graphene oxide composite materials

ABSTRACT

A composition includes at least one polymer doped with graphene oxide to induce conductivity in the polymer and at least one agent immobilized at least one of (i) on graphene oxide extending from the surface of the composite material or (ii) within the composite material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/433,389, filed Apr. 3, 2015, which is a national phase filing of PCTInternational Patent Application No. PCT/US2013/063421, filed Oct. 4,2013, which claims benefit of U.S. Provisional Patent Application Ser.No. 61/709,639, filed Oct. 4, 2012, the disclosures of which areincorporated herein by reference.

GOVERNMENTAL INTEREST

This invention was made with government support under grant nos. 0748001and 0729869 awarded by the National Science Foundation and grant no.R01NS062019 awarded by the National Institutes of Health. The governmenthas certain rights in this invention.

BACKGROUND

The following information is provided to assist the reader inunderstanding technologies disclosed below and the environment in whichsuch technologies may typically be used. The terms used herein are notintended to be limited to any particular narrow interpretation unlessclearly stated otherwise in this document. References set forth hereinmay facilitate understanding of the technologies or the backgroundthereof. The disclosure of all references cited herein are incorporatedby reference.

With advances in the preparation and characterization of graphene andgraphene oxide (GO), there has been growing interest in those materialsbecause of their outstanding electrical, physical and chemicalproperties. The application of graphene and GO for interacting withbiological systems has only been recently explored. To date, studiesevaluating the biocompatibility of graphene and GO have beeninconclusive, with some reports demonstrating severe dose-dependenttoxicity, while others indicate that graphene nanomaterials may enhancecell growth.

Another class of conductive organic material, conducting polymers(sometimes referred to herein as CP), has been extensively studied inbiological and biomedical fields such as biosensors, neural tissueengineering and neural electrodes. In these applications, it may bedesired to immobilize biologically active agents such as biomolecules tothe polymer to impart functionalities specific for interfacing with thebiological systems. Such modification often requires the substratematerial to have at least one derivatizable functional group, which manyof the conducting polymers, such as polyethylenedioxythiophene (PEDOT),lack. To add functional groups to a conducting polymer such as PEDOT,generally two strategies have been adopted. Using PEDOT as an example,one strategy is the direct addition of functional groups to the monomer3,4-ethylenedioxythiophene (EDOT), followed by polymerization of themodified EDOT monomer. This method requires tedious synthesis andpurification procedures for the modified EDOT monomers, and the addedfunctional groups may pose electronic and steric limitations duringpolymerization. Once again, using PEDOT as an example, the otherstrategy is the copolymerization of EDOT with other monomers ormolecules that possess functional groups. Although fairly simple, thismethod is still unsatisfactory because the presence of these moleculesmay impair the conductivity and stability of the resultant PEDOT.

Another method of imparting bioactive functionality to a conductivepolymer such as PEDOT is to dope the polymer with bioactive moleculesdirectly. Peptides, drugs and proteins have been directly incorporatedin PEDOT for neural interfacing or controlled drug delivery. However,only negatively charged biomolecules can be used as dopants and most ofthem are poor dopants because of their weak charge and large size. Poordopants lead to difficulty in electropolymerization and low conductivityof the resulting polymer. Furthermore, the biomolecules are entrappedthroughout the film, limiting the exposure of the functional domain atthe surface.

SUMMARY

In one aspect, a composition includes a composite material including atleast one conducting polymer doped with graphene oxide and at least oneagent immobilized at least one of (i) on graphene oxide extending fromthe surface of the composite material or (ii) within the compositematerial. In a number of embodiments, the at least one agent isimmobilized on graphene oxide extending from the surface of thecomposite material. The at least one agent may, for example, bechemically bonded to the graphene oxide or adsorbed on the grapheneoxide. In a number of embodiments, the at least one agent is covalentlybonded or ionically bonded to the graphene oxide.

In a number of embodiments, the at least one agent is releasablyimmobilized within the composite material. The at least one agent may,for example, be controllably released from within the composition viaapplication of electrical energy thereto.

The at least one agent may, for example, be an anionic agent, a cationicagent, a zwitterionic agent or a neutral agent. In a number ofembodiments, the at least one agent is a biologically active agent. Thebiologically active agent may, for example, include or be at least oneof a biomolecule or a drug.

The biologically active agent may, for example, include or be anamphetamine, a steroid, an anesthetic, an analgesic, an antacid, anantibiotic, an anticoagulant, an antidepressant, an antidote, anantihistamine, an anti-inflammatory, an antimycotic, an anticanceragent, an analgesic agent, an antirejection agent, an antiretroviral, anantiviral, a barbiturate, a beta blocker, a booster, a contraceptive, adecongestant, a depressant, an emetic, an expectorant, a hypnotic, animmunosuppressant, a laxative, a narcotic, a neurochemical, an opiates,a painkiller, a prophylactic, a purgative, a relaxant, a sedative, astatin, a suppressant, a tranquilizer, a vaccine or a vitamin.

In a number of embodiments, the biologically active agent is or includesa superoxide dismutase mimic, a porphyrin, a protein, an organiccatalyst, a nucleic acid, an organometallic, a glycoprotein, aglycosaminoglycan, a peptide, an aptamer, a polyamine, a polyamino acid,a cytokine, a carbohydrate, an oleophobic, a lipid, extracellularmatrix, a component of extracellular matrix, a growth factor, ahemostatic agent, a virus, a vireno, a virus vector, or a prion. In anumber of embodiments, the biologically active agent is or include acell adhesion molecule, an adhesive protein, a peptide, a cytokine or agrowth factor. In a number of embodiments, the biologically active agentis or includes an aptamer, an antibody, an enzyme, a ribozyme, DNA orRNA. The biologically active agent may, for example, be dexamethasone.

In general, any conductive polymer is suitable for use herein. In anumber of embodiments, the at least one conductive polymer is selectedfrom the groups of polypyrroles, polyanilines,poly(3,4-ethylenedioxythiophene), poly(fluorine)s, polypyrenes,polyazulenes, polynaphthalenes, polycarbazoles, polyindoles,polyazepines, poly(p-phenylene sulfide), polythiophenes, polyp-(phenylene vinylene), poly p-phenylene, and their derivatives.

In another aspect, a system includes a support and a composition asdescribed above deposited upon the support. In a number of embodiments,the support is an electrode. As described above, the compositioncomprising a composite material comprising at least one conductingpolymer doped with graphene oxide, and at least one agent immobilized atleast one of (i) on graphene oxide extending from the surface of thecomposite material or (ii) within the composite material. The at leastone agent may, for example, be as described above. Electrical circuitryor electronics may, for example, be in electrical connection with theelectrode to, for example, effect control, processing, analysis etc.

In a number of embodiments, the system is operable as a sensor fordetecting an analyte. The at least one agent may, for example,selectively interact with the analyte. In a number of embodiments, theat least one agent is a biologically active agent as described above. Ina number of embodiments, the biologically active agent is or includes asuperoxide dismutase mimic, a porphyrin, a protein, an organic catalyst,a nucleic acid, an organometallic, a glycoprotein, a glycosaminoglycan,a peptide, an aptamer, a polyamine, a polyamino acid, a cytokine, acarbohydrate, an oleophobic, a lipid, extracellular matrix, a componentof extracellular matrix, a growth factor, a hemostatic agent, a virus, avireno, a virus vector, or a prion. In a number of embodiments of sensorsystem hereof, the biologically active agent is or includes a celladhesion molecule, an adhesive protein, a peptide, a cytokine or agrowth factor. In a number of embodiments of sensor systems hereof, thebiologically active agent is or includes a superoxide dismutase mimic,an aptamer, an antibody, a protein such as an enzyme, or a nucleic acidsuch as a ribozyme, DNA or RNA.

In general, any conductive polymer is suitable for use in sensorshereof. In a number of embodiments, the at least one conductive polymeris selected from the groups of polypyrroles, polyanilines,poly(3,4-ethylenedioxythiophene), poly(fluorine)s, polypyrenes,polyazulenes, polynaphthalenes, polycarbazoles, polyindoles,polyazepines, poly(p-phenylene sulfide), polythiophenes, polyp-(phenylene vinylene), poly p-phenylene, and their derivatives.

In a number of embodiments, the system is operable to controllablyrelease the at least one agent which is immobilized within the compositematerial. In a number of embodiments, the at least one agent is abioactive agent as described above. The bioactive agent may, forexample, be or include a drug. The drug may, for example, be anamphetamine, a steroid, an anesthetic, an analgesic, an antacid, anantibiotic, an anticoagulant, an antidepressant, an antidote, anantihistamine, an anti-inflammatory, an antimycotic, an anticanceragent, an analgesic agent, an antirejection agent, an antiretroviral, anantivirals, a barbiturate, a beta blocker, a booster, a contraceptive, adecongestant, a depressant, an emetic, an expectorant, a hypnotic, animmunosuppressant, a laxative, a narcotic, a neurochemical, an opiates,a painkiller, a prophylactic, a purgative, a relaxant, a sedative, astatin, a suppressant, a tranquilizer, a vaccine or a vitamin.

In another aspect, a method of forming a composition includes forming acomposite material including at least one conducting polymer andgraphene oxide, wherein at least a portion of the graphene oxide extendsfrom a surface of the composite material. The composite material may,for example, be formed by polymerizing at least one conducting polymerin the presence of graphene oxide. In a number of embodiments, thecomposite is formed by electropolymerizing the at least one conductingpolymer in an aqueous solution comprising at least one monomer andgraphene oxide. The method further includes immobilizing at least oneagent upon graphene oxide extending from the composite material. The atleast one agent may, for example, be as described above. In a number ofembodiments, the at least one agent is a biologically active agent asdescribed above. The particle size of the graphene oxide may, forexample, be used/varied to control physical properties of thecompositions. For example, the particle size of the graphene oxide maybe used/varied to control at least one of the amount of agent in thecomposition, one or more electrical properties (for example,conductance, impedance etc.) of the composition, or the morphology ofthe composition.

In a number of embodiments, the at least one agent selectively interactswith an analyte. The composition may, for example, be adapted for use ina sensor for detecting the analyte.

In another aspect, a method of forming a composition includesimmobilizing graphene oxide and at least one agent in at least oneconducting polymer. In a number of embodiments, the method includespolymerizing at least one conducting polymer in the presence of grapheneoxide and the at least one agent such that the at least one agent andthe graphene oxide are immobilized within the conducting polymer. In anumber of embodiments, the method includes electropolymerizing the atleast one conducting polymer in an aqueous solution including at leastone monomer, graphene oxide and the at least one agent such that the atleast one agent and the graphene oxide are immobilized within theconducting polymer. The at least one agent may, for example, bereleasably immobilized within a composite material comprising theconducting polymer and the graphene oxide. The at least one agent may,for example, be as described above. In a number of embodiments, the atleast one agent is a biologically active agent as described above. Theparticle size of the graphene oxide may, for example, be used/varied tocontrol physical properties of the compositions. For example, theparticle size of the graphene oxide may be used/varied to control atleast one of the amount of agent in the composition, the rate of releaseof the agent, one or more electrical properties of the composition, orthe morphology of the composition. The at least one agent may, forexample, be controllably releasable from the composite material uponapplication of electrical energy thereto. For example, a biologicallyactive agent such as a drug may be controllably released uponapplication of electrical energy.

In a further aspect, a method includes providing a composition, whichincludes a composite material comprising at least one conducting polymerdoped with graphene oxide and at least one agent releasably immobilizedwithin the composite material, and applying an electric current to thecomposition to release the agent from the composite material. Asdescribed above, in a number of embodiments, the at least one agent is abiologically active agent such as a drug.

In still a further aspect, a method of forming a composition includesimmobilizing graphene oxide in at least one conducting polymer andcontrolling particle size of the graphene oxide to control at least oneproperty of the composition. In a number of embodiments, the methodincludes polymerizing the at least one conducting polymer in thepresence of graphene oxide, and controlling particle size of thegraphene oxide to control at least one property of the composition. In anumber of embodiments, the method includes electropolymerizing the atleast one conducting polymer in an aqueous solution comprising at leastone monomer and graphene oxide, and controlling particle size of thegraphene oxide to control at least one property of the composition.Particle size of the graphene oxide may, for example, be used, varied orpredetermined (for example, to be within a predetermined range ofparticle size) to control at least one of the amount of an agent in thecomposition, a rate of release of the agent from the composition, one ormore electrical properties of the composition or the morphology of thecomposition. Control of such properties is useful in, for example,controlling the operation of electrodes, sensors, agent deliverysystems, conductors, superconductors, etc. including the composition.

The present devices, systems, methods and compositions, along with theattributes and attendant advantages thereof, will best be appreciatedand understood in view of the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an SEM image of a representative, electrodepositedPEDOT/GO film, showing rough, network-like morphology of the surface,wherein the film was electropolymerized at 1.0 V for 600 s in 0.02 MEDOT solution containing 10 mg/mL GO (the scale bar in is 5 μm).

FIG. 1B illustrates an SEM image of the electrodeposited PEDOT/GO filmof FIG. 1A wherein the scale bar in is 1 μm.

FIG. 1C illustrates schematically a conductive polymer and a GO dopantdeposited on the surface of an electrode, with an agent bonded to the GOdopant.

FIG. 2 illustrates FTIR spectra of GO sheets synthesized using amodified Hummers method (lower curve) and electropolymerized PEDOT filmdoped with GO sheets (upper curve).

FIG. 3A illustrates viability of neurons growing on PEDOT films dopedwith GO or PSS at 24 hours, showing that PEDOT/GO films performsimilarly to control PEDOT/PSS films, exhibiting no loss of viability(the error bar represents SEM (n=5)).

FIG. 3B illustrates death of neurons growing on PEDOT films doped withGO or PSS at 24 hours, showing that PEDOT/GO films perform similarly tocontrol PEDOT/PSS films, exhibiting minimal cell death (the error barrepresents SEM (n=5)).

FIG. 4 illustrates an SEM image of a neuron growing on the PEDOT/GOsurface at 1 day, wherein the cell exhibits extensive neurite branchingand forms contacts with other cells, demonstrating the biocompatibilityof the PEDOT/GO film.

FIG. 5A illustrates neuron growth on a PEDOT surface doped with GO at 3days in a representative 20× fluorescent image of β-III-tubulinimmunofluorescent reactivity (green) of neurons.

FIG. 5B illustrates neuron growth on a PEDOT surface doped with PSS at 3days in a representative 20× fluorescent image of β-III-tubulinimmunofluorescent reactivity (green) of neurons.

FIG. 5C illustrates neuron density (±SEM, n=3) of cells growing on thepolymer surfaces.

FIG. 5D illustrates average neurite length (±SEM, n=3) of cells growingon the polymer surfaces, showing that the GO-doped PEDOT films supportneurons with longer neurites extensions than PSS doped PEDOT films (**p<0.01).

FIG. 6A illustrates high resolution XPS spectra of the PEDOT/GO surfaceafter treatment with p20 in conjugation with EDC/NHS, showingdeconvoluted peaks of the C1s region (C1: C—C; C2: C—O/C—S; C3: C—O—C;C4: N—C═O; C5: O—C═O).

FIG. 6B illustrates high resolution XPS spectra of the PEDOT/GO surfaceafter treatment with p20 in conjugation with EDC/NHS, showingdeconvoluted peaks of the N1s region (N1: C—N; N2: N—C═O; N3: protonatedamine).

FIG. 7A illustrates Bode plots of the electrochemical impedance behaviorof platinum iridium microwires: uncoated (circles), coated with PEDOT/GO(squares) and coated with PEDOT/GO covalently modified with p20(triangles).

FIG. 7B Nyquist plots of the electrochemical impedance behavior ofplatinum iridium microwires: uncoated (circles), coated with PEDOT/GO(squares) and coated with PEDOT/GO covalently modified with p20(triangles).

FIG. 8A illustrates neuron attachment and neurite outgrowth on PEDOT/GOsurfaces modified with p20 peptide at 24 hours in a representative 20×fluorescent image of β-III-tubulin immunofluorescent reactivity ofneurons cultured on a bare surface.

FIG. 8B illustrates neuron attachment and neurite outgrowth on PEDOT/GOsurfaces modified with p20 peptide at 24 hours in a representative 20×fluorescent image of β-III-tubulin immunofluorescent reactivity ofneurons cultured on a physically adsorbed p20 (p20 ADS) surface.

FIG. 8C illustrates neuron attachment and neurite outgrowth on PEDOT/GOsurfaces modified with p20 peptide at 24 hours in a representative 20×fluorescent image of β-III-tubulin immunofluorescent reactivity ofneurons cultured on a covalently immobilized p20 (p20 COV) PEDOT/GOsurface (the scale bar represents 50 μm and is applicable to FIGS.8A-8C).

FIG. 8D illustrates neuron density (±SEM, n=3) growing on the p20modified PEDOT/GO surfaces, showing that modification with p20 did notresult in a change in cell density.

FIG. 8E illustrates average neurite length (±SEM, n=3) of neuronsgrowing on the p20 modified PEDOT/GO surfaces (* p<0.05), showing thatcovalent immobilization, but not physical adsorption of p20 on the filmsurface enhanced neurite outgrowth.

FIG. 9A illustrates an embodiment of a superoxide dismutase mimic(SODm).

FIG. 9B illustrates that increased superoxide concentration results in alarger peak current when voltage of a sensor electrode including CP/GOwith adsorbed SODm is swept past its oxidation potential.

FIG. 10A illustrates a schematic representation of a DEX-loaded GO/PPynanocomposite film.

FIG. 10B illustrates a schematic representation of DEX release from theGO/PPy nanocomposite in response to electrical stimulation.

FIG. 10C illustrates a graph of cumulative release profiles of GO/PPynanocomposite in response to electrical stimulation (n=3).

FIG. 10D illustrates a representative fluorescent image of astrocytecultures exposed to no drug.

FIG. 10E illustrates a representative fluorescent image of astrocytecultures exposed to DEX released from GO/PPy nanocomposite films (rDEX).

FIG. 10F illustrates a representative fluorescent image of astrocytecultures exposed to prepared DEX solutions (DEX).

FIG. 10G illustrates a graph of the density of astrocyte cultures 4 daysafter exposure to drug treatment, wherein * indicates significantdifference from control (n=4, p<0.05).

FIG. 11A illustrates the effect of sonication on GO nanosheet and GO/PPynanocomposite properties in a histogram of sheet thickness after 30 minand 60 min sonication.

FIG. 11B illustrates the amount of DEX adsorbed by free GO sheets (***p<0.001; n=3).

FIG. 11C illustrates elemental analysis of DEX-loaded nanocompositefilm, wherein the F:N ratio reflects the amount of drug loaded into thefilm (** p<0.01; n=3).

FIG. 11D illustrates the amount of DEX released from nanocomposite filmsin response to 100 voltage pulses, showing that less sonication resultsin a faster release rate (* p<0.05; n=4).

FIG. 11E illustrates a schematic representation of the effect of GOsheet sonication on nanocomposite properties.

FIG. 12A illustrates the effect of GO sonication on GO/PPy filmmorphology in an SEM image of DEX-loaded GO/PPy films prepared with GOsonicated for 30 minutes, wherein the scale bar in is 30 μm.

FIG. 12B illustrates the effect of GO sonication on GO/PPy filmmorphology in an SEM image of DEX-loaded GO/PPy films prepared with GOsonicated for 30 minutes, wherein the scale bar in is 5 μm.

FIG. 12C illustrates the effect of GO sonication on GO/PPy filmmorphology in an SEM image of DEX-loaded GO/PPy films prepared with GOsonicated for 60 minutes, wherein the scale bar in is 30 μm.

FIG. 12D illustrates the effect of GO sonication on GO/PPy filmmorphology in an SEM image of DEX-loaded GO/PPy films prepared with GOsonicated for 60 minutes, wherein the scale bar in is 5 μm.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments, asgenerally described and illustrated in the figures herein, may bearranged and designed in a wide variety of different configurations inaddition to the described example embodiments. Thus, the following moredetailed description of the example embodiments, as represented in thefigures, is not intended to limit the scope of the embodiments, asclaimed, but is merely representative of example embodiments.

Reference throughout this specification to “one embodiment” or “anembodiment” (or the like) means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearance of the phrases “in oneembodiment” or “in an embodiment” or the like in various placesthroughout this specification are not necessarily all referring to thesame embodiment.

Furthermore, described features, structures, or characteristics may becombined in any suitable manner in one or more embodiments. In thefollowing description, numerous specific details are provided to give athorough understanding of embodiments. One skilled in the relevant artwill recognize, however, that the various embodiments can be practicedwithout one or more of the specific details, or with other methods,components, materials, et cetera. In other instances, well knownstructures, materials, or operations are not shown or described indetail to avoid obfuscation.

As used herein and in the appended claims, the singular forms “a,” “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “an agent” includes aplurality of such agents and equivalents thereof known to those skilledin the art, and so forth, and reference to “the agent” is a reference toone or more such agents and equivalents thereof known to those skilledin the art, and so forth.

GO possesses, for example, many oxygen containing functional groups,such as carboxyl, hydroxyl and epoxide, rendering it hydrophilic anddispersible in aqueous solutions. This property, along with itsabundance of negatively charged carboxyl groups, makes it an excellentdopant for the electropolymerization of conducting polymers. In additionto electropolymerization, other polymerization techniques as known inthe polymer arts may be used. Additionally, GO has recently been shownto act as a promoter of neuronal growth and maturation, making it aninteresting candidate as a neural interfacing material. Conductingpolymer/GO nanocomposites exhibit favorable electrical properties,energy storage and stability. In a number of embodiments hereof, methodsfor straightforward electrochemical synthesis of a conductive polymericmaterial doped with GO are provided. The conductive polymeric materialsmay be exclusively doped with GO. Unlike some previous GO-containingmaterials, the GO-doped conductive polymeric materials hereofdemonstrate biocompatibility. In a number of representative embodiments,PEDOT was doped with GO, and biocompatibility was demonstrated via invitro compatibility with neuronal cells.

The GO particles, sheets or nanosheets are partially entrapped by aconductive polymer such PEDOT on the surface of the nanocomposite andmany of functional groups such as carboxyl functional groups of GO onthe surface are exposed freely. The exposed functional groups of the GOenable immobilizing (via, for example, chemical bonding (for example,covalent or ionic bonding) or via adsorption) of an agent such asbiologically active agents (including, for example, biomolecules) to thefunctional groups of the GO. In a number of representative embodiments,biomolecule decoration on a PEDOT/GO film surface was demonstrated viacarbodiimide conjugation. In that regard, in several representativeembodiments, covalent immobilization of peptide RNIAEIIKDI (p20), andfunctional neurite outgrowth domain of extracellular matrix protein,laminin was demonstrated. The immobilization procedures described hereinand other straightforward reaction schemes may be universally appliedCP/GO composite materials/matrices and bioactive agents (including, forexample, bioactive proteins and peptides) for a variety ofbio-interfacing and other applications.

Reaction schemes other than carbodiimide conjugation may, for example,be used to chemically bond agents to exposed functional groups of GO ina CP/GO composite material. For example, to react with carboxylic acidgroup, one may also use SOCl₂ to form —CO—Cl which will then react withan amine group of an agent (for example, a protein or a peptide).Moreover, one may also use a biotin-streptavidin linkage. One may alsouse, for example, hydroxyl or OH functional groups on GO for chemicallybonding an agent to GO. For example, silane reagents or gluteraldehydemay be used for coupling to hydroxyl functional groups. Moreover, ionicbonding may also be used.

In a number of embodiments hereof, CP/GO composite materials are used torelease agents such a biologically active agent (including, for example,drug molecules) in a controlled manner. A number of representativeembodiments hereof demonstrate electrically controlled drug deliverysystem and methods based on GO nanosheets incorporated into a conductingpolymer or CP film. As described above, GO is a two-dimensionalnanomaterial composed of a honeycomb carbon lattice structure withfunctional groups, such as hydroxyl, carboxyl and epoxide functionalgroups and exhibits exceptional electrical, chemical, and mechanicalproperties. In a number of representative embodiments hereof, it wasdemonstrated that when incorporated into polypyrrole (PPy) along withanti-inflammatory drug, dexamethasone (DEX), the GO nanosheets create astable nanocomposite film that can release the drug molecules on-demandin response to electrical stimulation. Altering, for example, thethickness and size of the GO nanosheets changes the physical propertiesand release profile of the nanocomposite materials hereof, indicatingthat such systems may be tuned to the needs of various applications (forexample, implementation in therapeutic and exploratory research withinthe field of biomedicine).

As used herein, the terms “biologically active” or “bioactive” refergenerally to an agent, a molecule, or a compound that affects biologicalor chemical events in a host. Biologically active or bioactive agentsmay be synthetic molecules, biomolecules, or multimolecular entities andinclude, but are not limited to, proteins (including, but not limitedto, collagen, fibrin/fibrinogen, fibronectin, entactin, tenascin andenzymes (including, but not limited to, MMPs, TIMPs, proteinases,phospholipases, plasmin/plasminogen, lipases, and lysyl oxidase, acrosslinking agent for collagen)), organic catalysts, ribozymes,organometallics, glycoproteins (for example, proteoglycan),glycosaminoglycans (for example, hyaluronic acid or HA), peptides,aptamers, polyamines, polyamino acids, antibodies, nucleic acids,cytokines, carbohydrates, oleophobics, lipids, extracellular matrixand/or its individual components (such as collagen etc.), growthfactors, hemostatic agents (including, for example, small molecules suchas ATP and epinephrine and derivatives thereof), drugs, pharmaceuticals,chemotherapeutics, and therapeutics. Cells and non-cellular biologicalentities, such as viruses, virenos, virus vectors, and prions can alsobe bioactive agents. The term “biomolecule” refers any molecule that isproduced by a living organism, including large macromolecules such asproteins, polysaccharides, lipids, and nucleic acids, as well as smallmolecules such as primary metabolites, secondary metabolites, andnatural products.

In a number of embodiments, biologically active agents hereof include,but are not limited to, at least one of a protein, an organic catalyst,a nucleic acid (for example, RNA, DNA, a ribozyme etc.), anorganometallic, a glycoprotein, a glycosaminoglycan, a peptide, apolyamine, a polyamino acid, an antibody, a nucleic acid, a steroidalmolecule, an antibiotic, an anti-inflammatory, an antiviral, anantimycotic, an anticancer agent, an analgesic agent, an antirejectionagent, an immunosuppressant, a cytokine, a carbohydrate, an oleophobic,a lipid, extracellular matrix, an individual component of extracellularmatrix, a growth factor, a hemostatic agent, a virus, a vireno, a virusvector or a prion.

In a number of embodiments, the biologically active agent includesextracellular matrix or a component of extracellular matrix. Thebiologically active agent can also include a hemostatic agent. Forexample, the biologically active agent can include collagen, fibrin orplasmin. The biologically active agent may, for example, include ahemostatic agent such as a small molecule hemostatic agent (for example,ATP, a derivative of ATP, epinephrine or a derivative of epinephrine).

In several embodiments, the biologically active agent include a growthfactor, including, for example, EGF, TGFa, PDGF, VEGF, IGF-1, FGF, HGF,KGF, TGFb, a CXCR3 ligand, IL-10 or IL-4.

In several embodiments, the biologically active agent includes an agentselected to promote at least one of cell adhesion, cell proliferation orcell migration. The biologically active agent can, for example, includesites for binding of at least one of beta1 or beta3 integrins.

In a number of embodiments for directing cell attachment, growth anddifferentiation, the biologically active agents is a cell adhesionmolecule, an adhesive protein, a functional peptide, a cytokine or agrowth factor. In a number of embodiments for sensors, the biologicallyactive agent is an aptamer, an antibody, a superoxide dismutase mimic(SODm), an enzyme, a nucleic acid (for example, DNA, RNA or a ribosome).The term “aptamer” refers to oligonucleic acid or peptide molecules thatbind to a specific target molecule. Aptamers are excellentbiorecognition molecule for biosensors as a result of their highstability, high affinity, and reproducible chemical production. Aptamersof any biomolecular target molecule (or other agents which selectivelyinteract with an analyte) can be readily immobilized on an electrode ofany scale (from nano to micro to macro) in the sensors hereof. In thatregard, conducting polymer/graphene oxide composite materials are usedto facilitate the immobilization of, for example, aptamers on electrodeswhile enhancing the ability of electrode to detect the analyte by meansof electrochemical or electrical measurement. In a number ofembodiments, conducting polymers are electrodeposited using grapheneoxide as dopants. Functional groups such as carboxylic acid groups ofthe graphene oxide are then functionalized with an agent (for example,aptamer) of choice.

As used herein, the term “drug” refers to a substance which has aneffect (for example, a medicinal, intoxicating, performance enhancingand/or other effects) upon administration to a body of a human or otheranimal. Medicinal drugs, medicines or pharmaceuticals are chemicalsubstances used in treatment, cure, prevention or diagnosis of diseasesor used to otherwise enhance physical or mental well-being. Medicinaldrugs include, but are not limited to, amphetamines, steroids,anesthetics (for example, a topical or contact anesthetic), analgesicsor painkillers, antacids, antibiotics, anticoagulants, antidepressants,antidotes, antihistamines, anti-inflammatories, antimycotics,antimicrobials (for example, macrolide, a topoisomerase inhibitors or acephalosporin), anticancer agents, analgesic agents, antirejectionagents, antiretrovirals, antivirals, barbiturates, beta blockers,boosters, contraceptives, decongestants, depressants, emetics,expectorants, hypnotics, immunosuppressants, laxatives, narcotics,neurochemicals (neurotransmitters, modulators and inhibitors of neuraltransmission, agonists and antagonists of ion channels), opiates,prophylactics, purgatives, relaxants, sedatives, statins, suppressants,tranquilizers, vaccines and vitamins.

As used herein, the term “conducting polymer” refers to organic polymerthat conduct electricity. Conducting polymers include contiguous sp²hybridized carbon centers. The polymer chains may, for example, includearomatic cycles and/or double bonds. In general, any conductingpolymer(s) can be used herein. Example of suitable conducting polymersinclude, but are not limited to, polypyrroles, polyanilines,poly(3,4-ethylenedioxythiophene), poly(fluorine)s, polypyrenes,polyazulenes, polynaphthalenes, polycarbazoles, polyindoles,polyazepines, poly(p-phenylene sulfide), polythiophenes, polyp-(phenylene vinylene), poly p-phenylene, and their derivatives.

A number of representative embodiments are discussed below in which anagent is immobilized on exposed graphene oxide (that is, graphene oxideextending from the surface of a CP/GO composite material) or in which anagent is immobilized within the matrix of a CP/GO material. Moreover,various immobilization techniques (including, for example, covalentbonding, ionic bonding, adsorption) are also discussed. Agents may beimmobilized in a manner which is relatively resistant to release (forexample, via covalent bonding) or in a manner which is conducive torelease (for example, via adsorption in certain embodiments). Each ofthe various manners of immobilizing an agent or agents may, for example,be used exclusively or in combination in various embodiments hereof.

Immobilization of Agents on Exposed Graphene Oxide

GO was synthesized using the modified Hummers method and its micro ornanosheet morphology was confirmed with transmission electron microscopy(TEM). For PEDOT/GO film synthesis in a number of embodiments,electropolymerization of EDOT was carried out in aqueous solutioncontaining only EDOT and GO. In a number of representative examples, noadditional electrolyte was used to avoid the involvement of any dopantother than GO. In the presence of the negatively charged GO, EDOT wassuccessfully electropolymerized on the electrode surface, indicatingthat GO, itself, acts to sufficiently dope the polymer film. In a numberof representative embodiments, a GO concentration of 10 mg/ml wasutilized to maintain a conductive polymerization solution. In suchembodiments, because solutions containing lower amounts of GO resultedin slower or less charge passage during the polymerization reaction, arelatively high concentration of GO was selected to ensure adequate filmgrowth. The resulting film was uniform, and the incorporated GO createda network-like surface morphology (see, for example, FIGS. 1A and 1B).GO concentration may vary over a broad range, however. In a number ofembodiment, GO concentrations may, for example, range betweenapproximately 0.5 mg/ml and 20 mg/ml. The particle size of the GOparticles/sheet immobilized within a CP matrix hereof may vary broadly.In a number of embodiments, for example, the particles size ranges from10s of nanometers to 10s of microns.

FIG. 1C illustrates schematically a conductive polymer 10 and a GOdopant 20 after electropolymerization on the surface of an electrode100. An agent 200 is illustrates as, for example, covalently attached toexposed GO dopant 20 via a linking group 210 which is the reactionproduct/residue of a functional group of the unreacted agent and afunctional group of the unreacted GO. Agent 200 may also be attachedvia, for example, ionic bonding or sorption (for example, adsorption).The system of FIG. 1C further includes electronics of electroniccircuitry 300 (illustrated schematically in FIG. 1C) in operativeconnection with electrode 100 which may, for example, includecontrollers, processors, analytical systems etc. as known in theelectronics arts.

FTIR analysis of the synthesized GO sheets and the PEDOT/GO filmsverified successful incorporation of GO into the film (see FIG. 2). PureGO exhibits peaks at 3396 cm⁻¹, 1726 cm⁻¹, 1404 cm⁻¹, 1283 cm⁻¹, and1058 cm⁻¹ that represent carboxylic O—H stretching and vibration,carboxylic C═O stretching and vibration, O—H deformation, epoxy C—Ostretching and vibration, and alkoxy C—O stretching and vibration,respectively. The spectrum of the electrodeposited PEDOT/GOnanocomposite contains the characteristic peaks for C═O stretching andvibration of carboxyl groups at 1744 cm⁻¹ and O—H deformation at 1410cm⁻¹. As PEDOT polymer does not contain either carboxyl or hydroxylfunctional groups, the presence of such groups are attributable to GO,the sole dopant in the polymerization solution, indicating that the GOsheets have been successfully incorporated into the polymer film. Thepresence of the carboxylic carbonyl peak indicates that the filmcontains carboxylic acid functional groups provided by the GO sheetsthat may, for example, be utilized for agent (for example, bioactiveagent/biomolecule) immobilization with, for example, carbodiimidecrosslinking. The carboxylic O—H stretching and vibration band thatshould be apparent around 3400 cm⁻¹ is absent in the PEDOT/GO spectrum,and is likely obscured by the tail of the ˜1 eV bipolaron absorptionband, a typical attribute of conductive polymers

PEDOT doped with various molecules, such as heparin, poly(styrenesulfonate), (PSS) and adhesive peptides has been shown to be relativelynon-cytotoxic. However, soluble GO has demonstrated inconsistenttoxicity effects. The biocompatibility of GO incorporated in conductingpolymers has not previously been studied. To explore thecytocompatibility of the GO-doped conducting polymer film, the viabilityand death of neurons growing on the PEDOT/GO surface after 24 hours wereevaluated with the MTT viability and propidium iodide (PI) exclusionassays and compared to PEDOT films containing the commonly andextensively studied dopant PSS. To isolate the effects of the polymersurface directly on the cell viability/death, the surfaces were notcoated with laminin, an extracellular matrix protein widely used topromote neuron attachment and growth on various surfaces. There was nosignificant difference in viability between the PEDOT/GO and PEDOT/PSSfilms, with each group exhibiting greater than 96% of the metabolicactivity of neurons growing on a control TCP surface (FIG. 3A). Neuronsgrowing on the PEDOT/GO surface did not undergo a higher percentage ofdeath than the cells on the PEDOT/PSS surface (GO: 12.79±5.0; PSS:20.61±3.78, FIG. 3B).

A mechanism of soluble GO cytotoxicity shown in previous studies remainsunclear, but multiple processes have been suggested, including uptakeinto the cell or adsorption onto the cellular membrane and consequentapoptosis or death, disruption of membrane integrity and cellularexchange, interference with cell adhesion, or induction of oxidativestress. Without limitation to any mechanism, the absence of significantcytotoxicity caused by PEDOT/GO films in the present studies may arisefrom the entrapment of the GO sheets within the film, hindering theirability to diffuse within the culture media and interact freely with theneurons. Cells growing on the surface of the film are largely contactingthe PEDOT polymer, which has demonstrated biocompatibility with neuronalcells. The minimal toxicity of CP/GO materials such as PEDOT/GO filmsindicates that the nanocomposite materials have potential forbiological/medical use (for example, as neural interfacing materials).

To evaluate the neural biocompatibility of the PEDOT/GO composite, filmswere electrochemically deposited on gold sputtered coverslips. Theresulting PEDOT/GO coated coverslips were used as substrates to growprimary neuron cultures. SEM imaging revealed that neurons exhibitedhealthy growth on the surface of nanocomposite films in the absence oflaminin treatment (FIG. 4). Cells spread and flattened on the film andextended long, highly branched neurites that interconnected with otherneurons, demonstrating that the surface supported neural attachment andmaturation. Possibly as a result of the specific network-likemicrostructure of the PEDOT/GO film, some of the smaller processes ofneurons intimately grew along or around the partially exposed GO ridgeson the surface of the film, potentially using the film morphology as aguidance cue for neurite outgrowth. Representative fluorescent imagesshow neuron attachment and growth on PEDOT/GO and PEDOT/PSS films after3 days in culture (see FIGS. 5A and 5B). The neurons grew on the surfaceof the PEDOT/GO film at a density comparable to that of PEDOT/PSS,indicating that the GO is not specifically contributing any obstructionto the attachment of cells (see FIG. 5C). While previous GObiocompatibility studies have indicated that GO initiates downregulationof adhesion proteins, such as laminin, fibronectin, and focal adhesionkinase-1, leading to a decrease in cellular adhesion, data from thepresent studies suggest that GO entrapped in the polymer matrix may nothave such adverse effects on neuron attachment. These results agree witha proposed mechanism for decreased cell adhesion that attributes alteredgene expression to the activation of intracellular pathways after GOnanoparticles adhere to the cell membrane. GO sheets embedded in thePEDOT polymer matrix may, for example, be restricted from interactingwith the cell membrane in a way that would initiate changes in geneexpression, rendering the PEDOT/GO film a favorable surface for cellattachment and growth.

Neurons growing on the PEDOT/GO film exhibited significantly longerneurites than cells growing on the PEDOT/PSS film (FIG. 5D, GO: 36.4±2.0μm; PSS: 22.5±1.8 μm, p<0.01). Although the GO from the PEDOT/GO film islikely not being taken into the neuron cell body as a result of itsentrapment within the polymer matrix, its ability to strongly physicallyadsorb proteins (which is a consequence of the huge surface area of itssingle-layer carbon structure) may attract components of the cell mediato the surface of the polymer film, enhancing growth cone outgrowth.Additionally, neurons have been shown to be extremely responsive to avariety of topographical cues. In particular, surface roughness has beenshown to promote neurite extension. The rough, network-like surfacemorphology of the PEDOT/GO film (FIGS. 1 and 4), compared to the smoothand featureless surface of PEDOT/PSS at the same scale may, for example,contribute to the longer neurite outgrowth in PEDOT/GO as compared toPEDOT/PSS. Regardless of the mechanism, the desirable effect on neuriteoutgrowth demonstrates that PEDOT/GO films are an amenable material forsupporting neuronal growth and maturation, and may be useful substratesfor neural tissue interfacing applications.

The GO sheets on the top layer of the PEDOT/GO films are partiallyembedded, as demonstrated by the network-like morphology of the film(see FIG. 1A-1C), and the exposed portions of the GO, rich in carboxylgroups (see FIG. 2), provide the PEDOT/GO films with many freefunctional groups. Utilizing carbodiimide conjugation to modify thesefunctional groups, a method of bioactive agent/biomolecule patterning onconducting polymer films was demonstrated. In a number of representativeexamples, a laminin fragment peptide, p20, which is reported to promoteneurite outgrowth, was conjugated to the electrodeposited film. Thepeptide was covalently attached to the PEDOT/GO film through theformation of amide bonds between the carboxyl groups on the surface ofPEDOT/GO and the amine groups of the p20, with the assistance ofcrosslinkers EDC and NHS. The presence of p20 on the film aftercarbodiimide modification was verified by hydrolysis and amino acidquantification (5.37 pmol-mm⁻¹).

XPS analysis of the PEDOT/GO film evaluated the surface chemistry of thefilm after p20 immobilization with EDC/NHS (see FIGS. 6A and 6B). Thedeconvoluted C1s region (FIG. 6A) consists of 4 peaks in addition to themain C—C peak located at 284.8 eV, including a C—O/C—S peak at 285.6 eV,an epoxy C—O—C peak at 286.9 eV, a N—C═O peak at 288.2 eV and an O—C═Opeak at 288.8 eV. The PEDOT contributes to the C—S and C—O—C peaks, theGO sheets contribute to the C—O, C—O—C, and O—C═O peaks, and the peptidecontributes to the O—C═O and N—C═O peaks. Analysis of the C1s region ofthe PEDOT/GO film treated with p20 in the absence of EDC/NHS resulted ina similar deconvolution. During the amide bond formation in the presenceof EDC/NHS, a carboxylic acid provided by the GO reacts with an amine onthe peptide, resulting in a net gain of one amide bond and a net loss ofone carboxylic acid bond. However, since both the GO and peptide containcarboxylic acids, a comparison of the ratio of amide to carboxylic acidbetween the experimental groups cannot be used to verify the formationof covalent amide bonds between the peptide and the film with theaddition of EDC/NHS. The carboxylic acid signal of the GO sheets islikely variable across the film depending on the proportion of GOexposed to the surface versus embedded within the polymer matrix, so theratio of amide to carboxyl will not reflect the amount of covalentlyattached peptide. A more appropriate method of evaluating the amideformation is to monitor the ratio of amine to amide bonds. During thecovalent reaction, one amine in the peptide p20 reacts with a carboxylicacid group to form an amide bond, so there will be more amide and lessamine after the covalent treatment, as compared to the physicaladsorption treatment. A high-resolution scan of the N1s region of thefilm treated with p20and EDC/NHS revealed a peak centered at 388.9 eV,corresponding to the nitrogen in the peptide (FIG. 6B). Deconvolution ofthe N1s peak resulted in a C—N (amine) peak at amine peak at 401.8 eV.The amide/amine ratio is 0.58, compared to 0.19 in the absence ofEDC/NHS crosslinking, indicating that the EDC/NHS treatment producedcovalent linkages between the peptide and the PEDOT/GO film.

The electrical properties of the electrodeposited PEDOT/GO films beforeand after p20 immobilization were studied using EIS. As shown in FIG.7A, coating the electrode with the PEDOT/GO film resulted in decreasedimpedance across all frequencies measured. Without limitation to anymechanism, the significant impedance decrease may, for example, beattributed to an increase in the effective surface area of the electrodeas a result of the network-like surface microstructure of thenanocomposite polymer film. Longer deposition times resulted in aprogressive decrease in impedance, demonstrating the film properties maybe tuned as desired by controlling deposition parameters. At 1 kHz, afrequency relevant to single unit neural recording, the impedance isdecreased by an order of magnitude after the PEDOT/GO deposition,indicating that the film may be a beneficial microelectrode coating toimprove the recording and stimulation capability of neural electrodes.The Nyquist plot of the impedance (FIG. 7B) demonstrates that the baremetal has mostly capacitive behavior, as indicated by its steep linearcurve. The electrodes coated with PEDOT/GO films exhibit a knee thatseparates capacitive behavior at low frequencies and diffusive behavior,characterized by a more gradual slope, at higher frequencies. Theemergence of diffusion-dominated behavior may be attributed to thecreation of a diffusion barrier by the conducting polymer film. Afterimmobilization of p20 at the surface of the polymer film, the impedanceincreases slightly, a possible result of the creation of a nonconductivepeptide layer at the electrode surface; however, the impedance remainssignificantly lower than that of the bare metal electrode.

The bioactivity of the immobilized p20 was assessed in representativestudies with primary neuron culture on the functionalized PEDOT/GOfilms. After 24 hours in culture, neuron attachment and average neuritelength were quantified and compared among PEDOT/GO films unmodified withpeptide (bare), and films modified with p20 via physical adsorption orcovalent immobilization. Representative fluorescent images illustratingβIII-tubulin immunoreactivity and neurite outgrowth on each film areshown in FIGS. 8A-8C. While there are no differences in the density ofneurons attached to each film (FIG. 8D), the average neurite length (seeFIG. 8E) of the neurons grown on the PEDOT/GO films covalently modifiedwith p20 is significantly longer than that on the other two films (bare:14.29±0.63 μm; adsorption: 14.59±1.72 μm; covalent immobilization:20.48±1.45 p<0.05). This observation may, for example, be ascribed tothe effect of p20, which is the neurite outgrowth domain of lamininprotein, and has been shown to enhance neurite outgrowth whenincorporated into conducting polymer films as a dopant. In the studies,there was no discernable effect of p20 when physically adsorbed on thePEDOT/GO film. It is possible that the peptide did not retain itsbioactivity, potentially as a result of conformational changes as aconsequence of the physical adsorption onto the film that may obstructlaminin receptors on the neurons from binding to the peptide. Covalentanchoring of p20 to the PEDOT/GO film leaves most of the peptide free tointeract with the cell, preserving the bioactivity of the peptide. It isalso possible that the physically adsorbed peptide desorbs over thecourse of the cell culture experiment, resulting in less neuriteoutgrowth. The covalently conjugated p20 is very stable and continues tosupport neurite outgrowth after presoaking in PBS at 37° C. for 3 daysprior to neuron culture (data not shown). This simple method offunctionalizing GO doped CP materials such as PEDOT films with bioactiveagents/biomolecules and its superior effectiveness over traditionalbiomolecule adsorption clearly demonstrates the potential of thenanocomposite materials hereof as a bio-interfacing material.

Electrodeposited CP/GO films showed good conductivity, and they cansignificantly lower the impedance of the coated electrodes. The CP/GOfilms possess a network-like surface structure as a result of thepresence of partially embedded GO sheets. Further CP/GO compositematerials support the growth of cells such as neurons with minimaltoxicity. Partially exposed GO pieces on the surface of the CP/GO filmsare rich in free functional groups such as carboxyl groups, which offerthe CP/GO films active functional groups for surface modification. Inthe representative embodiments discussed herein, a functional lamininpeptide, p20, was bioconjugated to the surface of a PEDOT/GO filmthrough a simple crosslinking reaction. However, that reaction and otherthat may be universally applied to a multitude CP/GO materials andbioactive agents. CP/GO materials thus provide excellent modifiabilityfor use, for example, in biological and biomedical applications (forexample, in neural interfacing and in biosensing).

In a representative embodiment of a sensor hereof, an analyte isdetected via a sensor comprising a compound/moiety immobilized uponexposed GO in a CP/GO material which interacts with the analyte. In anumber of embodiments, an enzyme is attached to GO in a CP/GO materialto detect a substrate (the analyte) for the enzyme. For example,glutamate oxidase enzyme may be immobilized upon a CP/GO material (forexample, PEDOT/GO), which is deposited upon an electrode, for thesensing of glutamate.

Reactive oxygen species may, for example, be sensed using a CP/GO (forexample, PEDOT/GO) material modified by physical adsorption ofsuperoxide dismutase mimic (SODm). The SODm may alternatively bechemically (for example, covalently) bonded to the CP/GO compositematerial. An SODm is illustrated in FIG. 9A. SODm is an antioxidantmetalloproteinase with a Mn core metal. The Mn is redox active and canbe oxidized and reduced in response to a voltage sweep. This redoxactivity is the basis of the SODm antioxidant properties. In thepresence of superoxide, the SODm will accept an electron, moving to itsreduced state (see FIG. 9B), and converting the superoxide to oxygen.One can create a superoxide sensor by adsorbing the SODm onto thesurface of the CP/GO film. When there is a larger amount of superoxidein a solution, there will be a larger amount of reduced SODm on theelectrode, and when the voltage is swept past its oxidation potential, alarger peak current is observed (see FIG. 9B). Reactive oxygen speciemay also be detected via, for example, a CP/OG composite including aphysically adsorbed porphyrin such as hemin.

On-Demand Release of Immobilized Agents

On-demand release of an agent (for example, drug molecules frombiomedical devices) enables precise, targeted application/dosing of theagent that can be temporally tuned to meet requirements for a variety ofapplications (for example, therapeutic applications). Recent advanceshave facilitated the use of various cues, such as UV- andvisible-wavelength light, NIR radiation, magnetic field, ultrasound andelectrical stimulation to trigger drug release in vivo from implantedsmart materials. These techniques provide greater control overtraditional in vivo drug release systems that rely on passive deliverythat is programmed prior to implantation and cannot be modified inresponse to changing therapeutic needs. To achieve precise, controlleddrug delivery, nanomaterial drug carriers are increasingly investigatedbecause of their unique structures and tunable properties.

The huge surface area and sp² hybridized carbon lattice associated withcarbon nanomaterials, such as carbon nanotubes, graphene, and grapheneoxide (GO), enables highly efficient loading of agents such as drugs,while their capacity for modification provides a route to targetagent/drug delivery and controllably release agents such as drugmolecules. In a number of compositions hereof, an electricallycontrolled agent delivery system includes GO nanosheets incorporatedinto a conducting polymer (CP) film/matrix. The agent to be delivered isreleasably immobilized within the film/matrix.

As described herein, nanocomposite films consisting of GO micro- ornanosheets and CPs demonstrate favorable electrical properties, goodstability, neuronal biocompatibility and ease of surface modificationwith bioactive molecules. These properties, along with the low cost andsimple synthesis of GO micro- or nanosheets (sometimes referred toherein collectively as nanosheets or simply sheets), make the GO/CPcomposite material/film an interesting candidate as a novel material forelectrically controlled agent (for example, biologically activeagent/drug) release.

During CP film polymerization, negatively charged species are typicallyloaded into the polymer matrix to balance positive charges formed on thebackbone of the growing polymer. GO sheets are negatively charged as aconsequence of carboxylic acid groups formed at their edges during theoxidation procedure, enabling them to be incorporated into the CP filmas dopant molecules along with, for example, agents such as drugmolecules (FIG. 10A).

In a number of representative embodiments, it was demonstrated that whenincorporated into polypyrrole (PPy) along with anti-inflammatory drug,dexamethasone (DEX), GO nanosheets create a stable nanocomposite filmthat can release the drug molecules on-demand in response to electricalstimulation. In a number of studies, the DEX-loaded GO/PPy (GO/PPy-DEX)films were potentiostatically electrodeposited onto glassy carbonelectrodes from a solution containing both GO nanosheets and DEX. Duringthe electropolymerization reaction, the GO nanosheets compete with theanionic DEX as dopant molecules. Various factors, including moleculesize and number of charges, may affect dopant incorporation into CPfilms. GO is a comparatively large structure with multiple negativecharges, suggesting that it may not dope the film as readily as thesmaller, more mobile DEX molecule that contains only two negativecharges. Fourier-transform IR (FTIR) spectrum of the GO/PPy-DEX filmdisplays peaks attributable to both GO and DEX, indicating that the drugmolecules are successfully loaded into the film along with thenanosheets. The synthesized nanocomposite exhibited low impedance andhigh charge storage capacity, reflecting the favorable electroactivityof the film; as these properties decrease and increase, respectively,more current will pass through the film in response to a particularvoltage pulse, enabling more efficient drug release.

Electrically controlled release of various agents, includingbiologically active agents/molecules may, for example, be achieved byutilizing the unique red-ox properties of GO/CP-releasable agentcomposite materials such the representative GO/PPy-DEX nanocompositefilms hereof. In that regard, when the film is oxidized, negativelycharged agents (for example, drug molecules) remain within the materialto balance the positively charged polymer backbone. Reduction of thematerials elicits the release of anionic dopant agents as the polymerbackbone becomes neutrally charged.

To evaluate its performance as a drug-releasing film, voltage pulseswere applied through the GO/PPy-DEX nanocomposite immersed in PBS, andthe release solution was analyzed with UV absorbance spectroscopy toquantify the amount of DEX expelled from the film. Application ofnegatively polarized voltage stimulation to the GO/PPy-DEX filminitiated the release of DEX molecules from the film, while the GOnanosheets remained entrapped within the polymer matrix (see FIG. 10B).Large dopant molecules are generally immobile within CP films,suggesting that GO nanosheets, which may, for example, measure hundredsof nanometers to microns in the x-y direction, remain within the CPduring film reduction. Small quanta of drug can be repeatedly releasedfrom the GO/PPy film in response to electrical stimulation (−0.5 V for 5s followed by 0.5 V for 5 s in several representative embodiments),creating a drug release profile that is linear over several hundredstimulations. However, no observable drug passively diffused from thefilm in the absence of stimulation (see FIG. 10C). Moreover, there wasno cracking or delamination of the GO/PPy film visible after undergoingrepeated electrical stimulation, indicating that the nanocomposite hasgood electrochemical stability. The persistent linear release profileaccompanied by good film stability is important, for example, inapplications in which chronic, temporally precise drug dosing isrequired.

The bioactivity of the released representative drug was assessed byadding solutions containing DEX released from GO/PPy films to primaryastrocyte cultures and evaluating the extent of interruption in cellproliferation. DEX is a synthetic glucocorticoid (GC) that is commonlyused to treat inflammation and is used here as a model drug todemonstrate the capacity of the release system. Chronic DEX exposure hasbeen shown to interrupt astrocyte proliferation, likely bydownregulating glucocorticoid receptor expression. Astrocyte culturesexposed to the release solutions exhibited a significantly lowerpopulation of cells after 4 days of growth as compared to controlcultures that received no drug treatment (FIGS. 10D-G, p<0.05). The celldensity of the release solution-treated culture was not significantlydifferent than that of a culture that was exposed to a prepared DEXsolution at a known concentration of 1 μM. These data indicate that theprocess of incorporation into and electrically stimulated release fromthe nanocomposite film does not significantly alter the bioactivity ofagents such as DEX molecules. To address the potential release of anytoxic byproducts from the GO/PPy film, release solutions were applied toprimary neuron cultures. No effect on neuron growth was visible after 2days of exposure, indicating that the interruption of astrocyte growthwas a result of specific actions of DEX, rather than non-specificcytotoxicity from components of the GO/PPy film (for example, monomer orGO nanosheets) that may have delaminated from the electrode duringelectrical stimulation.

During chemical synthesis of GO, oxidized graphite sheets are commonlyexfoliated with ultrasonication to obtain single- and few-layer GO(s/fGO). During sonication, the sheets are also reduced in the x-ydimension to create a smaller particle size on the order of hundreds ofnanometers. To investigate the effect of altering the GO nanosheet sizeon the properties of the nanocomposite, the GO suspension was submittedto 30 or 60 min of sonication immediately prior to incorporation intothe film. When the GO suspension undergoes longer sonication treatment,the distribution of the nanosheet thickness shifts to smaller values,indicating that the sheets are exfoliated into more s/fGO sheets (seeFIG. 11A). GO nanosheets may have enhanced utility as drug nanocarrierscompared to other materials because their large surface area and sp²hybridized carbon structure enables efficient loading via adsorption of,for example, aromatic drug molecules, such as DEX. As multi-layer GO isexfoliated into thinner s/fGO particles, a larger amount of GO surfacearea is created within the suspension, supporting a higher level ofagent adsorption onto the free GO nanosheets (FIGS. 11B and 11E).

Elemental analysis of the DEX-loaded nanocomposite films provides asemi-quantitative summary of the amount of drug loaded into the film. Inthat regard, each DEX molecule contains one fluorine atom and eachsubunit of PPy contains one nitrogen atom. Thus, the ratio of fluorineatoms to nitrogen atoms in the film corresponds to the amount of drugloading. As expected, nanocomposite films synthesized with GO sonicatedfor 60 min load more drug than the films synthesized with GO sonicatedfor 30 min, as indicated by the F:N ratio (FIG. 11c , p<0.01). Withoutlimitation to any certain mechanism, FIG. 11E depicts the proposedmechanism by which controlling GO sonication time can tune drug loadinginto the polymerized nanocomposite, creating a level of flexibility thatcan meet the dosing needs of a particular application. Therepresentative, drug-loaded GO/PPy nanocomposite may beelectropolymerized from an aqueous solution containing free GO sheetsand DEX molecules (and/or other agent(s)), creating an opportunity forthe drug to load onto the surface of the nanosheets prior to filmdeposition. With more sonication treatment, more GO sheets are presentin the polymerization suspension as each multi-layer GO particle isexfoliated into several s/fGO sheets. Prior to electrodeposition, the GOsheets load some DEX molecules onto their surfaces through physicaladsorption, then compete with the remaining free DEX molecules asdopants during the polymerization reaction. As GO undergoes sonication,the nanoparticle size decreases in the z-direction (FIG. 11A) and thex-y-direction, creating smaller particles that act as more efficientdopant molecules. Additionally, as each multi-layered GO exfoliates intomultiple s/fGO particles, there will be a larger number of interactivenanosheet edges containing negatively charged carboxylic acid groups.This should lead to more GO nanosheets depositing into the nanocompositefilm, and because each GO sheet can carry multiple drug molecules intothe film, a larger total amount of DEX can be loaded as a result ofincreased sonication treatment. Likewise, a larger amount of an agentmay be immobilized upon exposed GO particles in the embodiment discussedabove.

Interestingly, although increased GO sonication leads to more efficientdrug loading into the nanocomposite, a significant change in the rate ofDEX released from the film in response to voltage pulse stimulation wasobserved (FIG. 11D, p<0.05). After 100 stimulations, the nanocompositesynthesized with GO sonicated for 60 min released 38% less DEX than the30 min sonication group. Without limitation to any mechanism, the strongadsorption of DEX molecules onto the GO sheets prior to depositionwithin the film may be the driving mechanism behind the slowed drugrelease rate (see FIG. 11E). It is possible that the DEX moleculesadsorbed onto the GO surface cannot be as easily released from the filmas directly doped DEX molecules as a result of the strength of the π-πinteractions, limiting the amount of drug release in response to thesame electrical stimulation. Regardless of any underlying mechanism, theunique properties of the GO/CP composite materials such as GO/PPynanocomposites may be utilized to create highly tunable release systemswith the ability address various dosing needs for a multitude of agentdelivery applications.

Along with providing control over drug loading and release, the GOnanosheets create a unique opportunity to alter the morphologicalcharacteristics of nanocomposite materials such as film. For example,sonication had a significant effect on the morphology of the DEX-loadedGO/PPy film (see FIG. 12A-12D). With less GO sonication, the filmexhibited globular, cauliflower-like features on the scale of tens ofmicrons that are characteristic of PPy films. As the amount of GOsonication increased from 30 min to 60 min, the large globular featuresflattened to create a more uniform surface (see FIG. 12A and 12C).Without limitation to any mechanism, the large features are possibly aresult of nucleation sites created by the multi-layer GO nanoparticles.As the nanoparticles deposit into the film, they may provide a scaffoldaround which the growing polymer can accumulate. With longer sonicationtime, the smaller s/fGO may distribute more evenly in the film, creatinga smoother surface (FIG. 11E). At a smaller scale, as the sonicationtime increases, small sheet-like features became more apparent at thesurface of the film, suggesting that more GO sheets were incorporatedinto the nanocomposite (see FIGS. 12B and 12D). At the 60 min sonicationtime point, the sheet-like features reduced in size to sub-microndimensions, as would be expected because increased sonication treatmentfractures GO sheets into smaller particles. The ability to subtly alterthe nanocomposite surface morphology at different length scales may, forexample, have important implications for applications in which the filminteracts with tissue or cells. Multiple cell types have demonstratedsensitivity toward mechanical and topographical cues in theirenvironment, suggesting that the nanocomposite film morphology may beengineered, for example, to act synergistically with the electricallycontrolled drug release to provide additional signals to the targetedcell population.

The GO sheets thus provide several degrees of customizability to theelectrically controlled agent (for example, drug) release platformshereof. By altering the size and thickness of the nanosheets,significant changes can be made to the film morphology, agent load andagent release properties. As a nanocarrier, GO enables loading of avariety of agents (including, for example, bioactive agents such asbiomolecules), not limited to anionic species, into the materials (forexample, films). Furthermore, the GO/CP nanocomposite materials exhibita linear release profile that persists over many (for example, severalhundred) stimulations, indicating that the release platform may be usedin, for example, chronic drug release and other applications thatrequire repeated release/dosing of an agent over time.

On-demand controlled drug delivery provides more effective therapieswith less toxicity by tuning delivery directly to spatial and temporalrequirements for a given application. In addition, controlled deliverymay be beneficial in various in vitro assays, such as high-throughputdrug screening or exploratory cell biology experimentation. Because oftheir adjustable properties, stability, and fine control over dosing,the GO nanocomposite release platforms described herein have thepotential to advance such drug delivery technologies by enablingtailored drug release profiles over a range of dosage requirements.

Agents (including biologically active agents other than drugs) otherthan anionic agents may also be releasably immobilized within CP/GOcomposite materials hereof. For example, cationic species (for example,dopamine, acetylcholine, Na+, K+, Mg++ and Ca++) may be ionically bondedto the carboxylic acid groups on GO, or on an additional polyaniondopants. When a positive electrical current is applied, the negativespecies on the polyanion dopant or on the GO will interact with theconducting polymer backbone while cationic species will be released. ForZwitterionic molecules, it is possible to adjust the media pH and pushthe molecules to either negative or positively charged. For neutralmolecules releasably immobilized or entrapped within a CP/GO compositematerial hereof, it is possible to force or “squeeze” the neutral agentout of the CP/GO composite material as a result of electrical actuationof the CP/GO films. For example, electrically induced oxidation andreduction always accompany ionic and water movement in or out of thefilm, which leads to shrinkage and expansion. Such volumetric andporosity change can be used to allow entrapped molecules to be released.

Experimental Examples

Materials. Graphite powder was purchased from Bay Carbon Inc. (SP-1, BayCity). 3,4-Ethylenedioxythiophene (EDOT),poly(sodium-4-styrenesulfonate) (PSS, Mw˜70,000), phosphate bufferedsaline (PBS, pH 7.4, 10 mM sodium phosphate and 0.9% NaCl),glutaraldehyde (25% in H₂O), osmium tetroxide (OsO₄, 4 wt. % in H₂O),hexamethyldisilazane (HMDS),1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), andN-Hydroxysuccinimide (NHS) were purchased from Sigma-Aldrich. Thepeptide RNIAEIIKDI (p20) was synthesized at the University of PittsburghPeptide Synthesis Facility. All other chemicals were of analyticalgrade, and Milli-Q water from a Millipore Q water purification systemwas used throughout.

Electrodeposition. GO was synthesized through the oxidization ofgraphite powder according to the modified Hummers method, andcharacterized using transmission electron spectroscopy (TEM) (JEOLJEM-2100F). The Hummers method is, for example, described in W. S.Hummers and R. E. Offeman, J Am Chem Soc, 80, 1339-1339 (1958) and N.Mohanty and V. Berry, Nano Lett, 2008, 8, 4469-4476, the disclosure ofwhich are incorporated herein by reference. PEDOT/GO films wereelectrodeposited onto platinum/iridium (Pt/Ir) microelectrodes (standardtip, diameter: 2-3 μm, MicroProbes, Gaithersburg, Md.) forelectrochemical characterization or gold sputtered plastic microscopecoverslips (macroelectrode area: 0.38 cm²) for surface characterizationand cell culture using a Gamry Potentiostat, FAS2/Femtostat (GamryInstruments, Warminster, Pa.) with Gamry Framework software. Aconventional three-electrode system with the Pt/Ir or gold electrodeacting as the working electrode, a platinum foil as the counterelectrode, and a silver/silver chloride (Ag/AgCl) reference electrode(CH Instruments, Austin, Tex.) was used. The PEDOT/GO waselectropolymerized from an aqueous solution containing 0.02 M EDOT and10 mg/mL GO. PEDOT/PSS films were synthesized from anelectropolymerization solution containing 0.02 M EDOT and 0.1 M PSS. Aconstant potential of 1.0 V was applied to achieve a charge density of200 nC total for microelectrodes or 100 mC/cm² for macroelectrodes.

Modification of PEDOT/GO with p20. The peptide p20 was covalentlyimmobilized on the surface of the PEDOT/GO coated electrodes through anamine reaction between carboxyl groups on the GO and amine groups on thepeptide. The PEDOT/GO electrodes were incubated in a solution of 0.2mg/ml p20, 0.2 M EDC and 0.2 M NHS in sterile H₂O for 3 h at roomtemperature, and then thoroughly washed with sterile PBS to remove anyfree p20, EDC or NHS. In another set of samples, PEDOT/GO films wereincubated with p20 in the absence of EDC/NHS as a control for physicaladsorption. The amount of p20 on the surface of the covalently modifiedPEDOT/GO film was quantified using amino acid hydrolysis followed byhigh performance liquid chromatography.

Electrochemical Impedance Spectroscopy. The electrochemical impedancespectroscopy (EIS) was measured with an Autolabpotentiostat/galvanostat, PGSTAT128N (Metrohm Autolab) with Nova 1.8software using a three-electrode system with a platinum foil counterelectrode and Ag/AgCl reference electrode. The EIS was measured in PBSin the frequency range from 10 Hz to 100 kHz using an alternatingcurrent sinusoid of 20 mV in amplitude with the direct current potentialset to 0 V.

PEDOT/GO Film Surface Analysis. The surface of PEDOT/GO films wascharacterized using Fourier transform infrared (FTIR) spectroscopy,scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy(XPS). FTIR measurements were carried out using a Bruker Vertex 70spectrometer equipped with a Hyperion 2000 microscope. A 20× attenuatedtotal reflectance (ATR) objective was employed to record the spectra ofdeposited thin films. The ATR spectra were converted to transmittancespectra via the standard method within the spectrometer operationsoftware package, OPUS 6.5.

The surface morphologies and microstructures of the PEDOT/GO films wereexamined with an XL30 SEM (FEI Company) operated at 10 kV. Samples withneurons growing on the surface were analyzed with the same SEM, but at alower operating potential of 5 kV. Samples with cells were treated with2.5% glutaraldehyde and 1% OsO4, both for one hour in sequence, followedby dehydration. The dehydration was performed by soaking the samples in30% and 50% ethanol in PBS, 70% and 90% ethanol in water, and 100%ethanol in sequence for 15 min each, followed by immersion in HMDS for15 min.

XPS analysis of PEDOT/GO films after treatment with p20 in the presenceor absence of EDC/NHS was performed with a K-Alpha XPS system (ThermoScientific) equipped with a monochromated Al K₆₀ source (1486.68 eV).High resolution scans of the C1s and N1s regions were taken at twolocations on each sample.

Primary Neuron Culture. PEDOT/GO coated macroelectrodes were fixed tothe surface of 24-well culture plates with Kwik-Sil (World PrecisionInstruments) and sterilized with exposure to UV light for 15 min.Following sterilization, the polymer surfaces were washed with sterilePBS. Cortical tissue was isolated from E18 Sprague-Dawley rat embryosand treated with 0.025% Trypsin in a digestion buffer containing 137 mMNaCl, 5 mM KCl, 7 mM Na₂HPO₄, and 25 mM HEPES. Neurons were dissociatedwith gentle tritruation and maintained in Neurobasal medium (Invitrogen,21103-049) supplemented with B27 (Invitrogen, 17504-044), GlutaMax(Invitrogen, 35050-061) and Antibiotic-Antimycotic (Invitrogen15240-062). For neuron growth assays, cells were seeded on PEDOT/GO andPEDOT/PSS surfaces at a density of 100 k cells per electrode and grownfor 3 days. For neuron viability and death assays, polymer samples werecut to fit into 96-well plates and seeded with neurons at a density of10 k per well. For the cell cultures intended to assess the p20functionalization on PEDOT/GO films, similar procedures were followed.In order to measure the neurite length easily by preventing theformation of very long and interconnected neurites, neurons were seededon the PEDOT/GO surfaces at a density of 100 k cells per electrode andgrown for only 24 h before fixation and immunocytochemical analysis.

Immunofluorescence Staining and Quantification. Neurons growing on thepolymer surfaces were fixed in 4% paraformaldehyde in PBS for 15 min andwashed several times with PBS. The cells were immersed in a blockingbuffer (5% goat serum/0.2% triton-X in PBS) for 20 min followed byincubation in mouse monoclonal antibody against β-III-tubulin (TuJ1,1:1000, Sigma) for 1 h. After washing in PBS, the cells were incubatedin goat anti-mouse Alexa Fluor 488 (1:1000, Invitrogen) secondaryantibody for 1 h, washed in PBS and counterstained for nuclei usingHoechst 33342 (Invitrogen).

TuJ1-immunoreactive cells were imaged using a fluorescence microscope.For each experimental group, 10 random 10× images were collected fromeach sample (n=3). Neuron density was quantified by counting the numberof TuJ1-immunoreactive cells that extended at least one neurite thatmeasured longer than the width of the cell body. Neurite analysis wasperformed using the NeuronJ plugin for ImageJ (a public domain JAVA®language image processing program) downloadable from the Unites StatesNational Institutes of Health. Neurites extending from each TuJ1+ cellbody were traced and measured, and the average neurite length wascalculated.

Neuron Viability and Toxicity Assay. The viability of neurons growing onthe PEDOT/GO composite and PEDOT/PSS films, as indicated by theirmitochondrial activity, was assessed with the MTT Cell ProliferationAssay Kit (Molecular Probes). The ratio of absorbance signal at 570 nmto 630 nm (reference wavelength) was used to assess metabolic activity.All polymer samples were normalized to a blank containing the polymersample with no cells, and compared to a positive control containingcells growing on the tissue culture polystyrene (TCP) well surface.

Percentage of cell death was assessed using the propidium iodide (PI)assay. PI fluoresces after binding to the nuclear material of deadcells, while the plasma membrane of healthy cells excludes the dye.Polymer samples were prepared and neuron culture performed as in the MTTassay. Fluorescence was evaluated in a spectrometer with an excitationat 530 nm and emission at 618 nm. Polymer samples were normalized tocontrols containing the same polymer with 100% dead cells, and comparedto cells growing on the TCP control surface.

Electrochemical Apparatus. All electrochemical experiments wereperformed with a Gamry Potentiostat, FAS2/Femtostat (Gamry Instruments)using a three-electrode set-up with glassy carbon (GC) workingelectrodes (3 mm diameter, CH Instruments), a platinum wire coil counterelectrode, and a silver/silver chloride reference electrode (CHInstruments).

Nanocomposite Film Synthesis. As described above, GO was synthesized bythe modified Hummers method as previously described. PPy films wereelectrochemically synthesized on the GC electrodes from an aqueoussolution containing 0.2 M pyrrole (Sigma-Aldrich) and 10 mg ml⁻¹dexamethasone 21-phosphate disodium salt (DEX, Sigma-Aldrich) and GOnanosheets (5 mg ml⁻¹). The GO suspension was ultrasonicated for 30 minimmediately prior to electropolymerization, unless otherwise noted. Aconstant potential of 0.8 V was applied until the charge density reached400 mC cm⁻¹.

Film Characterization. The surface morphology and microstructure wasevaluated with scanning electron microscopy (SEM, JEOL JSM6510). Filmsurface chemistry was evaluated with attenuated total reflectanceFourier transform IR (ATR-FTIR, Bruker Vertex 70). Elemental analysiswas performed by energy-dispersive X-ray spectroscopy (EDS, Oxford INCAEDS). Film roughness (R_(a)) and GO nanosheets thickness were evaluatedwith atomic force microscopy (AFM, Bruker Dimension V SPM).

Electrically Controlled Drug Release. All drug release experiments werecarried out in PBS. Films were submitted to square-wave biphasic voltagepulses of −0.5 V for 5 s followed by 0.5 V for 5 s. The PBS solutionscontaining the released drug were analyzed with UV spectroscopy at awavelength of 242 nm to quantify the amount of DEX release. To determinetotal amount of drug release, films underwent aggressive voltage pulses(−2 V for 5 s followed by 0 V for 5 s) until cumulative drug releaseplateaued. This value was used to calculate percentage of drug releasereported in FIG. 11D.

DEX Loading Capacity Assay. The amount of DEX loaded on GO sheets wasevaluated by incubating 100 μM DEX with 0.5 mg ml⁻¹ GO in H₂O for 2 h atroom temperature. Prior to incubation with DEX, the GO suspension wassonicated for 30 min or 60 min. The mixture was centrifuged for 30 minat 14,000 RPM to pellet the DEX-loaded GO nanosheets, and thesupernatant was analyzed with UV spectroscopy at 242 nm to determine theamount of DEX remaining in solution. The amount of drug loaded wascalculated by subtracting the amount of free DEX in the supernatant fromthe amount of DEX in a sample not incubated with GO.

Bioactivity Assay. To determine the bioactivity of released DEX,astrocyte cultures were exposed to release solutions for 4 d then fixedand immunostained for glial fibrillary acidic protein (GFAP). Detailedcell culture and immunofluorescence methodology are described in thesupporting information.

Statistical Analysis. All statistical analyses were carried out in SPSSsoftware. Student's t-tests were utilized for comparisons of twoexperimental groups and one-way analysis of variance (ANOVA) testsfollowed by Bonferroni's post hoc analysis or Tukey's post hoc analysiswere utilized for comparisons of more than two experimental groups.Statistical significance was considered for p<0.05 (*) and p<0.01 (**).All data is presented as the mean (±SEM).

The foregoing description and accompanying drawings set forth a numberof representative embodiments at the present time. Variousmodifications, additions and alternative designs will, of course, becomeapparent to those skilled in the art in light of the foregoing teachingswithout departing from the scope hereof, which is indicated by thefollowing claims rather than by the foregoing description. All changesand variations that fall within the meaning and range of equivalency ofthe claims are to be embraced within their scope.

What is claimed is:
 1. A composition, comprising: at least one polymerincluding contiguous sp² hybridized carbon centers and doped withgraphene oxide to induce conductivity in the polymer; and at least oneagent immobilized at least one of (i) on graphene oxide extending fromthe surface of the polymer or (ii) within the polymer.
 2. Thecomposition of claim 1 wherein the at least one agent is immobilized ongraphene oxide extending from the surface of the composite material. 3.The composition of claim 2 wherein the at least one agent is chemicallybonded to the graphene oxide or adsorbed on the graphene oxide.
 4. Thecomposition of claim 1 wherein the at least one agent is releasablyimmobilized within the composite material via application of electricalenergy thereto.
 5. The composition of claim 2 wherein the at least oneagent is an anionic agent, a cationic agent, a zwitterionic agent or aneutral agent.
 6. The composition of claim 2 wherein the at least oneagent is a biologically active agent.
 7. The composition of claim 6wherein the biologically active agent comprises at least one of abiomolecule or a drug.
 8. The composition of claim 6 wherein thebiologically active agent comprises an amphetamine, a steroid, ananesthetic, an analgesic, an antacid, an antibiotic, an anticoagulant,an antidepressant, an antidote, an antihistamine, an anti-inflammatory,an antimycotic, an anticancer agent, an analgesic agent, anantirejection agent, an antiretroviral, an antiviral, a barbiturate, abeta blocker, a booster, a contraceptive, a decongestant, a depressant,an emetic, an expectorant, a hypnotic, an immunosuppressant, a laxative,a narcotic, a neurochemical, an opiates, a painkiller, a prophylactic, apurgative, a relaxant, a sedative, a statin, a suppressant, atranquilizer, a vaccine or a vitamin.
 9. The composition of claim 6wherein the biologically active agent comprises a superoxide dismutasemimic, a porphyrin, a protein, an organic catalyst, a nucleic acid, anorganometallic, a glycoprotein, a glycosaminoglycan, a peptide, anaptamer, a polyamine, a polyamino acid, a cytokine, a carbohydrate, anoleophobic, a lipid, extracellular matrix, a component of extracellularmatrix, a growth factor, a hemostatic agent, a virus, a vireno, a virusvector, or a prion.
 10. The composition of claim 6 wherein thebiologically active agent comprises a cell adhesion molecule, anadhesive protein, a peptide, a cytokine or a growth factor.
 11. Thecomposition of claim 8 wherein the biologically active agent comprisesan aptamer, an antibody, an enzyme, a ribozyme, DNA or RNA.
 12. Thecomposition of claim 1 wherein the at least one polymer is selected fromthe groups of polypyrroles, polyanilines,poly(3,4-ethylenedioxythiophene), poly(fluorine)s, polypyrenes,polyazulenes, polynaphthalenes, polycarbazoles, polyindoles,polyazepines, poly(p-phenylene sulfide), polythiophenes, polyp-(phenylene vinylene), poly p-phenylene, and their derivatives
 13. Amethod of functionalizing a polymer composition with at least one agent,comprising: doping at least one polymer with graphene oxide to induceconductivity, wherein graphene oxide extends from the surface of thepolymer or is within the polymer; and immobilizing at least one agentupon graphene oxide.
 14. The method of claim 13 wherein the polymer isdoped by polymerizing the at least one conducting polymer in thepresence of graphene oxide.
 15. The method of claim 13 wherein thecomposite material is formed by electropolymerizing the at least onepolymer in an aqueous solution comprising at least one monomer andgraphene oxide.
 16. The method of claim 13 wherein the at least oneagent is an anionic agent, a cationic agent, a zwitterionic agent or aneutral agent.
 17. The method of claim 13 wherein the at least one agentis a biologically active agent.
 18. The method of claim 17 wherein thebiologically active agent comprises at least one of a biomolecule or adrug.
 19. The method of claim 17 wherein the biologically active agentcomprises an amphetamine, a steroid, an anesthetic, an analgesic, anantacid, an antibiotic, an anticoagulant, an antidepressant, anantidote, an antihistamine, an anti-inflammatory, an antimycotic, ananticancer agent, an analgesic agent, an antirejection agent, anantiretroviral, an antivirals, a barbiturate, a beta blocker, a booster,a contraceptive, a decongestant, a depressant, an emetic, anexpectorant, a hypnotic, an immunosuppressant, a laxative, a narcotic, aneurochemical, an opiates, a painkiller, a prophylactic, a purgative, arelaxant, a sedative, a statin, a suppressant, a tranquilizer, a vaccineor a vitamin.
 20. The method of claim 17 wherein the biologically activeagent comprises a superoxide dismutase mimic, a porphyrin, a protein, anorganic catalyst, a nucleic acid, an organometallic, a glycoprotein, aglycosaminoglycan, a peptide, an aptamer, a polyamine, a polyamino acid,a cytokine, a carbohydrate, an oleophobic, a lipid, extracellularmatrix, a component of extracellular matrix, a growth factor, ahemostatic agent, a virus, a vireno, a virus vector, or a prion.
 21. Themethod of claim 17 wherein the biologically active agent comprises acell adhesion molecule, an adhesive protein, a peptide, a cytokine or agrowth factor.
 22. The method of claim 17 wherein the biologicallyactive agent comprises an aptamer, an antibody, an enzyme, a ribozyme,DNA or RNA.
 23. The method of claim 17 wherein the biologically activeagent is dexamethasone.
 24. The method of claim 13 wherein particle sizeof the graphene oxide is used to control at least one of the amount ofagent in the composition, electrical properties of the composition, orthe morphology of the composition.
 25. The method of claim 13 whereinthe at least one polymer is selected from the groups of polypyrroles,polyanilines, poly(3,4-ethylenedioxythiophene), poly(fluorine)s,polypyrenes, polyazulenes, polynaphthalenes, polycarbazoles,polyindoles, polyazepines, poly(p-phenylene sulfide), polythiophenes,poly p-(phenylene vinylene), poly p-phenylene, and their derivatives 26.The method of claim 13 wherein the at least one agent selectivelyinteracts with an analyte.